Sb2Te3/graphene heterostructure for broadband photodetector: A first-principles calculation at the level of Cooper’s exchange functionals

Abstract

Low optical absorption and large energy band gap in the material utilized as an absorbing layer prevented a report of high-performance broadband photodetector. However, integrating antimony telluride (Sb2Te3) with graphene in a heterostructure appear to be the more promising approach to overcome the said issues. In this heterostructure, optical absorption takes place in Sb2Te3 while graphene acts as charge carrier collector owing to its high carrier mobility. Hence, detailed knowledge of the electronic and optical properties of Sb2Te3/graphene heterostructure, is essential to expose its hidden potentials. In this study, electronic and properties of Sb2Te3 surface states ad Sb2Te3/graphene heterostructure are presented using first-principles approach based on density functional theory (DFT) framework within the most recent developed Coope's exchange (vdW-DFC09x). Our surface states band structure calculations show that Sb2Te3 has metallic behaviour as its valence and conduction bands are found to be overlapped when the film thickness is four quintuple layers (QLs). The energy analysis of Sb2Te3/graphene heterostructure reveals that the most stable configuration is the one in which the Te-1 atom of Sb2Te3 facing to graphene is above the hole center of graphene's hexagonal lattice. More attractively, the system of Sb2Te3/graphene heterostructure shows that strong hybridization between Sb2Te3 and graphene at smaller interlayer distance resulted in an energy gap at the Dirac states. The Results of optical absorption show that Sb2Te3/graphene heterostructure has strong absorption in the near infrared to ultraviolet wavelenghts, therefore, it can be used in optoelectronics devices like optical communication, biomedical imaging, remote sensing, and gas sensing.